<!DOCTYPE html>
<html lang="en">
<head>
    <script src="../vue.js"></script>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    <button v-on:click="sayHello">Click this</button>
</div>

<script>
    let vm = new Vue({
        el: "#app",
        data: {
            message: "java"
        },
        methods: {
            sayHello: function() {
                alert(this.message);
            }
        }
    })
</script>
</body>
</html>